Mapping and analysis of changes in the riparian landscape structure of the Lockyer Valley catchment, Queensland, Australia

Abstract

A case study of the Lockyer Valley catchment in Queensland, Australia, was conducted to develop appropriate mapping and assessment techniques to quantify the nature and magnitude of riparian landscape structural changes within a catchment. The study employed digital image processing techniques to produce land cover maps from the 1973 and 1997 Landsat imagery. Fixed and variable width buffering of streams were implemented using a geographic information system (GIS) to estimate the riparian zone and to subsequently calculate the landscape patterns using the Patch Analyst (Grid) program (a FRAGSTATS interface). The nature of vegetation clearing was characterised based on land tenure, slope and stream order. Using the Pearson chi-square test and Cramer's V statistic, the relationships between the vegetation clearing and land tenure were further assessed. The results show the significant decrease in woody vegetation areas mainly due to conversion to pasture. Riparian vegetation corridors have become more fragmented, isolated and of much smaller patches. Land tenure was found to be significantly associated with the vegetation clearing, although the strength of association was weak. The large proportion of deforested riparian zones within steep slopes or first-order streams raises serious questions about the catchment health and the longer term potential for land degradation by upland clearing. This study highlights the use of satellite imagery and geographic information systems in mapping and analysis of landscape structural change, as well as the identification of key issues related to sensor spatial resolution, stream buffering widths, and the quantification of land transformation processes.

Six decades of changes in the riparian corridor of a Mediterranean river: a synthetic analysis based on historical data sources

“…Bertoldi et al, 2011a;Bertoldi et al, 2011b). The analysis of such sequences of historical imagery provides an opportunity to quantify large-scale features at a landscape scale and extract a variety of integrative metrics (Apan et al, 2002;Fernandes et al, 2011). Nevertheless, aerial images are insufficient to reveal small-scale features (local-level approach), such as plant species and community types (Braatne et al, 2008;Aguiar et al, 2010).…”

Riparian vegetation metrics as tools for guiding ecological restoration in riverscapes

“…Riparian areas are composed by patches, i.e. homogenous areas with different dynamics that can be distinguish within the riparian zone (Apan et al, 2002). The concept of landscape structure and riparian patches has been only applied recently (Apan et al, 2002) and few studies have been published (Fernandes et al, 2011).…”

“…homogenous areas with different dynamics that can be distinguish within the riparian zone (Apan et al, 2002). The concept of landscape structure and riparian patches has been only applied recently (Apan et al, 2002) and few studies have been published (Fernandes et al, 2011). Remote sensing has been used to map and characterize riparian vegetation features such as the percentage of canopy cover, canopy continuity and tree clearing Johansen and Phinn, 2006), buffer capacity (Ivits et al, 2009), width (Hyatt et al, 2004) and strata complexity (Johansen et al, 2007).…”

“…However, the coarse spatial resolution of the images that have been used and the mismatch between the riparian buffer considered and the real riparian area lead to errors in the estimation of these parameters (Schuft et al, 1999;Congalton et al, 2002;Yang, 2007). Landscape metrics, numeric descriptors that quantify patch configuration and the spatial relationships among patches, can be used to characterize the structure of riparian vegetation and help to make informed decisions on restoration planning, such as revegetating the riparian zones (Apan et al, 2002). These metrics can be related with general ecological processes and dynamics of riparian zones and express the ecological condition of riparian woods (Table I).…”

“…The priorization of areas in potential need to enhance, preserve or restore is fundamental since economic resources are limited and frequently areas to manage are large and are difficult of access. Forman and Godron, 1981;Forman, 1995 andApan et al, 2002).…”